The invention relates to apparatus for converting one pulse pattern into another pulse pattern and, more particularly, to apparatus for generating nonlinear pulse patterns from a linear pulse pattern.
In the performance of experiments, for example, an event will occur that should be detected and measured. For example, two characteristics that might or should be measured are the time and energy of the event. Typically, the event is measured by charging a capacitor to a voltage proportional to the time or energy of the event and then linearly discharging the capacitor to a predetermined level. Pulses are then generated during the discharging of the capacitor and are counted by a counter with a number of pulses counted being directly proportional to the capacitor voltage and the count stored in memory. Consequently, this count provides information, concerning the time or energy of the event.
There are occasions when, for example, the counter capacity and memory are too small for the time or energy range of interest of the event. Larger capacity counters and memory can be used to accommodate the large range, but this is costly.
Nonlinear pulse pattern generators have been developed which increase the range of measurement of the event without employing the larger capacity counters and memory. For example, U.S. Pat. No. 3,566,095 discloses a digital system in which a nonlinear pulse pattern is generated from a linear pulse pattern. This system counts the pulses of the linear pattern, in which the count is proportional to the characteristic of the event being measured, and generates output pulses of a nonlinear pattern so that there are proportionally fewer output pulses as the range of the event being measured gets larger. Specifically, this system generates output pulses at intervals of occurrence proportional to the square root of the number of pulses of the linear pattern that have been counted between the zero axis crossings of a signal.
A disadvantage with the generator of the above-mentioned U.S. patent is that it can generate only one nonlinear pulse pattern from the linear pulse pattern. As just mentioned, the specific nonlinear pulse pattern that can be produced by this generator is proportional to the square root of the number of pulses of the linear pattern which are counted between the zero axis crossings of a signal. Consequently, this generator is not flexible in that it may not be suitable for measuring characteristics of different events having different ranges of interest.
Also, other nonlinear pulse pattern generators are known which are specifically designed to generate a logarithmic pulse pattern from an input linear pulse pattern. A logarithmic pulse pattern has wide applicability in view of the fact that, for example, many naturally occurring events whose characteristics are to be measured have a logarithmic function. Two examples of logarithmic pulse pattern generators are disclosed in U.S. Pat. No. 4,089,060 and a publication entitled "A Logarithmic Time Based Generator or Counter," by Trump, et al, Rev. Sci. Instrum., Vol. 45, No. 5, May, 1974.
While the above and other logarithmic pulse pattern generators produce logarithmic patterns, they have the disadvantage of reducing what are known as truncating errors by waiting a fixed period after the start of the pulses of the linear clock pulse pattern before generating the logarithmic pulse pattern. That is, these prior logarithmic pulse pattern generators utilize counters which, initially, are caused to count to a preset count before the logarithmic pulse pattern begins to be produced. This preset count constitutes an undesirable delay that is introduced in these generators. The above-mentioned publication, for example, states that truncation errors may be minimized by making this delay as large as possible.
Furthermore, the above logarithmic pulse generators have the disadvantage of producing logarithmic patterns to only a limited number of log bases. For example, the generator of the above publication can produce logarithmic patterns which are to the log base a/(a-1). This means that the practical limits of this system can produce logarithmic patterns only from log base 1 to log base 2 for very large values of "a" down to a=2, respectively. A value of "a" less than 2 is impractical in this system because the next lower number would be a=1 and the value for a/(a-1) would be infinity.
It is an object of the present invention to provide a novel nonlinear pulse pattern generator and a novel logarithmic pulse pattern generator.
It is another object of the present invention to produce digital nonlinear and logarithmic pulse pattern generators which can be used to measure different events over large ranges of interest for a system of limited data capacity.
A further specific object of the present invention is to produce a nonlinear pulse pattern generator which can generate different nonlinear pulse patterns from a single linear pulse pattern, and to produce a logarithmic pulse pattern generator which is not limited in number of log bases to which patterns can be generated.
Another object of the present invention is to provide a logarithmic pulse pattern generator which reduces truncating errors without a delay in producing the pattern.